220 



U.S. NATIONAL MUSEUM BULLETIN 282 



RECENT 

 PLEISTOCENE 



z 



PLIOCENE 1^ 



MIOCENE^ 



OLIGOCENE ^ 



EOCENE)^ 



\ \\\V(// ^ 



fi -si ll ^ 



lull I 



i/'^^j.'-' — / / 



,>>^'^'' |Pylodictis| |Saton| 



Phytogeny of the Ictoluridoe 



Figure 5. — Phylogeny of the Ictaluridae. 



The species assigned to the subgenus Schilbeodes are more divergent 

 and possibly a heterogeneous assemblage. Prominent generalized 

 characters are found in a number of species. Those with a terminal 

 mouth and ten preoperculomandibular pores (gyrinus, lachneri, and 

 exilis) are very generalized with gyrinus being most primitive as 

 judged from its pelvic fin and deeply grooved pectoral spine. In this 

 area, A^. exilis has diverged considerably with nine pelvic rays and a 

 serrated spine. Noturus leptacanthus with eight pelvic rays and a 

 nonserrated spine may be the most primitive of those with an in- 

 cluded lower jaw, but Noturus insignis, Noturus -phaeus, and Noturus 

 funebris with modally seven hypurals retain a generalized character 

 that may be as significant. Noturus gilberti is probably the most 

 highly specialized member of the subgenus. Noturus fiavus, in the 

 subgenus Noturus, resembles gilberti in a number of characters but 

 is the only member of the genus constantly retaining the primitive 

 imfused pectoral radials ; however it has diverged considerably from the 

 generalized condition with specialization of the teeth and increase 

 in the number of paired fin rays and caudal rays. 



In the interpreted phylogeny (fig. 5), only a few of the species of 

 Ictalurus are indicated, otherwise the forms are arranged in natural 

 groups. The solid lines indicate the history as judged from fossils; 

 the dashed lines show the hypothetical history. 



